Method for preparing metal powder and method for evaluating raw material or diluting salt for use therein

Abstract

The present invention provides a method for producing a tantalum or niobium powder which controls releasing and contamination of impurities such as Fe, Ni, Cr, and Mo, which are derived from a reaction vessel, to a range in which characteristics of tantalum or niobium are not influenced. The method for producing a tantalum or niobium powder of the present invention is a method in which a metal salt containing tantalum or niobium is reduced in a diluent salt to obtain a tantalum or niobium powder, wherein a total percentage of moisture in the metal salt and the diluent salt is 0.2% by mass or less, as determined by the Karl Fisher method based on an amount of moisture generated by heating the metal salt and the diluent salt to 600° C.

1 . A method for producing a tantalum or niobium powder in which a metal salt containing tantalum or niobium is reduced in a diluent salt to obtain a tantalum or niobium powder, 
 wherein the total percentage of moisture in the metal salt and the diluent salt is 0.2% by mass or less as determined by the Karl Fisher method based on an amount of moisture generated by heating the metal salt and the diluent salt to 600° C.    
   
   
       2 . A method for producing tantalum or niobium powder according to  claim 1 , wherein the diluent salt is potassium fluoride or a mixture containing potassium fluoride, and the moisture percentage in potassium fluoride alone is 0.15% by mass or less, as determined by the Karl Fisher method.  
   
   
       3 . A method for producing tantalum or niobium powder according to  claim 1 , wherein the diluent salt is potassium chloride or a mixture containing potassium chloride, and the moisture percentage in potassium chloride alone is 0.05% by mass or less, as determined by the Karl Fisher method.  
   
   
       4 . A method for producing tantalum or niobium powder according to  claim 1 , wherein the metal salt is tantalum potassium fluoride, and the moisture percentage in tantalum potassium fluoride alone is 0.1% by mass or less, as determined by the Karl Fisher method.  
   
   
       5 . A method for producing tantalum or niobium powder according to  claim 1 , wherein the metal salt is niobium potassium fluoride, and the moisture percentage in potassium fluoride alone is 0.1% by mass or less, as determined by the Karl Fisher method.  
   
   
       6 . An anode for an electrolytic capacitor comprising the metal powder produced by the method of  claim 1 .  
   
   
       7 . A method for evaluating a metal salt containing tantalum or niobium used for producing a tantalum or niobium powder, wherein a moisture percentage in a metal salt is measured based on an amount of moisture which is generated by heating the metal salt to 600° C. or more.  
   
   
       8 . A method for evaluating a diluent salt used for producing a tantalum or niobium powder, wherein a moisture percentage in a diluent salt is measured based on an amount of moisture which is generated by heating the diluent salt to 600° C. or more.